1. Field of the Invention
The invention relates to a process and apparatus for forming from string a simple loop knot either through or about a product, and more particularly to a process and apparatus whereby the loop knotting step and other steps may be performed to produce individual products continuously, automatically and at a high production rate.
2. Description of The Prior Art
While the loop knotting process and apparatus of the present invention may have many uses, as will be discussed hereinafter, for purposes of an exemplary showing, they will be described with respect to their application in the manufacture of tampons of the type taught in U.S. Pat. 3,815,601, issued to Jean E. Schaefer on June 11, 1974 and commonly owned by the assignee of the present application. In accordance with the teachings of that patent, the tampon comprises an aggregate composed of individual pieces of absorbent, foam-like material encased within a flexible, fluid-permeable overwrap. The overwrap is in the nature of a tubular sack gathered and sealed at one end, and gathered and closed at the other end by a withdrawal string passed through the gathered overwrap material and formed into a simple loop knot.
Prior art workers have developed numerous knot forming machines for various purposes, as exemplified by U.S. Pat. Nos. 3,166,035 -- 3,434,441 and 3,583,131. The knots formed may be complex in nature or very simple utilizing preformed endless loop ties.
For the most part, prior art workers have affixed withdrawal strings to tampons by means of a simple loop knot. In some instances the loop knot has been formed transversely of and around the longitudinal center of a web of absorbent material and the web is thereafter folded upon itself to form a finished tampon. This is taught, for example, in U.S. Pat. Nos. 2,934,068 -- 3,011,495 -- 3,063,453 and 3,477,102. In other instances the loop knot has been formed through the absorbent material as taught in U.S. Pat. Nos. 3,131,435 and 3,606,643.
Unlike the prior art, however, the apparatus and process of the present invention converts a continuous tube of overwrap material having spaced apart, measured increments of aggregate or like material located therein and glue stripes printed thereon between the spaced, measured increments of aggregate material into individual sacks. Each sack is pleated at its ends. One end of the sack is sealed, while the other end of the sack is gathered and closed by a withdrawal string formed into a loop knot passing therethrough.
The apparatus of the present invention is characterized by remarkable simplicity and a high production rate. The apparatus comprises a rotating drum carrying a plurality of identical heads. Each of the heads is provided with a number of operating instrumentalities performing in sequence the process steps of the present invention. The apparatus operates upon a continuous web or tube of overwrap material and utilizes a single, continuous, external string source.